Folia Theologica 17. (2006)

Hugh Barbour: Salvare Apparentia

SALVARE APPARENTIA

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derline the urgency of resolving this doubt, it is sufficient to note that Aquinas explicitly includes the matters discussed in the first three books of his Summa contra gentiles among the truths defensible with demonstrativae vel probabliles rationes.

The example par excellence of an argument which St. Thomas holds is rationally demonstrative is, of course, his argument for the existence of God. The presentation of this argument is given in its most complete form in the thirteenth chapter of book one of the Summa contra gentiles. It is an argument which he describes earlier in the ninth chapter as totius operis necessarium fundamentum. Toward the end of the thirteenth chapter St. Thomas points out that two things seem to weaken the argument from motion for the existence of God which he has elaborated. Firstly, the whole argument as taken from Aristotle is based on the supposition of the eternity of the world, which for Catholics is an inadmissible doctrine. Secondly, the argument presupposes a primum mobile, an animate first and outermost sphere which is the "locator" and ultimate context of all the movement of the cosmos, which many, Aquinas says, do not concede. (It is interesting to note that here he does not describe the notion of the animate primum motum as contrary to Catholic faith, but he does declare it to be so in his commentary on the De caelo) Let us hear what he has to say about these apparently debilitating aspects of this argument.

First he speaks to the suppostion of the eternity of the world:

Ad hoc dicendum quod via efficacissima ad probandum Deum esse est ex suppostione aternitatis mundi, qua posita, minus videtur esse manifestum quod Deus sit. Nam si mundus et motus de novo incoepti, planum est quod oportet poni aliquam causam quae de novo producat mundum et motum; quia omne quod de novo fit ab aliquo innovatore oportet sumere originem; cum nihil educat se de potentia in actum, vel de non esse in esse.

Here St. Thomas argues that, even though the suppostion is false, and even in view of the revealed truth of creation in time, it still provides the most efficacious foundation for the argument for the existence of God. There could be no clearer indication than this that the rationality of his argument does not depend on the truth of the cosmological system of which he makes use, nor of the independence of Catholic theology from any given cosmology. What